Storage unit with rates of advance dependent on upstream and downstream rates

ABSTRACT

A storage unit for the temporary storage of rolls, arranged between a first section and a second section of a production line, is described which includes an endless flexible member defining a closed path within the storage unit and bearing a plurality of seats for the rolls, the seats being subdivided into a first group of empty seats and a second group of full seats; an input feeder for controlled distribution of rolls arriving from the first section to the seats of the first group; an output feeder for controlled discharge of rolls from the seats of the second group toward the second section; a first motor for advancing the seats of the first group toward the input feeder and; a second motor for advancing the seats of the second group toward the output feeder. The first and second motors have first and second independently adjustable continuous speeds, respectively. Further, the first and second motors move the flexible member at a continuous but variable speed. The first and second speeds are dependent on the rate of roll arrival from the first section and the rate of roll request from the second section, respectively.

TECHNICAL FIELD

The invention relates to a storage unit for the temporary storage ofrolls or logs of rolled up band-shaped material, arranged between afirst section and a second section of a production or conversion line.

More particularly, the invention relates to an intermediate storage unitof the type comprising: input means for the distribution in the storageunit of rolls arriving from said first section, output means for thecontrolled discharge of rolls from the storage unit towards said secondsection, an indefinite flexible member bearing a plurality of seats forsaid rolls, said seats being subdivided into two groups, of full seatsand of empty seats respectively, and two motor units, for the advance ofthe seats of the first group towards the output means and of the seatsof the second group towards the input means.

STATE OF THE ART

Temporary accumulation storage units of this type are described forexample in the U.S. Pat. Nos. 4,142,626 and 4,168,776. These arenormally used in paper conversion lines, in which, from a reel of paperof large diameter, small rolls of toilet paper, all-purpose towels andsimilar products are formed, which are packed in individual or multiplepackagings. In these conversion lines, the initial reel of paper isunrolled and rolled up again, in a so-called re-reeling machine, to formlogs or rolls of a height equal to the height of the reel and of adiameter equal to the diameter of the finished product. The logs thusobtained have to be closed by means of gluing of the free end in agluing machine arranged downstream of the re-reeling machine.Successively, each log or roll is sent to a cropper to be cutperpendicularly to its own axis to obtain small rolls of desired height.

Arranged between the gluing machine (or a number of gluing machines inparallel) and the cropper (or a number of croppers in parallel) is astorage unit for the temporary accumulation of the glued rolls whichmakes it possible to free the production rates of the re-reeling machineand of the gluing machine (or of the gluing machines) from that of thecropper or of the croppers. The storage unit has a pair of parallelchains forming an indefinite flexible member bearing a plurality ofoscillating seats or troughs which receive and discharge the rolls.

The flexible member of the accumulation storage unit, constituted by apair of parallel chains lying in two vertical planes on the two sides ofthe storage unit, are typically guided between series of guide wheels,some of which have a fixed axle and others have a movable axle, to allowa variation in the number of full and empty seats respectively. Thenumber of full seats varies in relation to the number of empty seatsaccording to the frequency of arrival of rolls from the productionsection upstream, and to the frequency of discharge of the rolls towardsthe section downstream. In traditional devices, the movement of theflexible member is of intermittent type, both in the input zone and inthe output zone. The actuation of the input and output motor units isbrought about respectively by the arrival of a roll from the gluingmachine or by the request for one or a number of rolls simultaneously bythe cropper. This intermittent movement causes a series ofdisadvantages, due mainly to the great dynamic stresses caused by thestarts and by the stops of the flexible member and of the full and emptyseats.

The control of the advance of the flexible member is particularlyimportant. In fact, it is necessary to ensure that all the seats ortroughs of the storage unit, on passage from the charging station, arefilled, without leaving empty seats intercalated with full seats. Thepresence of an empty seat between two full seats may bring about theabsence of a roll in one of the channels of the cropper and therefore anunbalance in the section of the line downstream, with consequent seriousdisadvantages in the packaging machines positioned downstream of thecropper. Correct functioning of the accumulation storage unit istherefore essential to avoid blockages of the line with consequent lossof production and mechanical disadvantages as a result of the necessityof stopping and restarting mechanical members of great mass andtherefore with great inertia. Given that modern paper conversion lineswork at a speed which can reach 1000 m/min, with a band of paper whichmay have a width of 2-5 m, with production rates up to 35 rolls aminute, a stoppage, even short, of the line means a considerable loss ofproduction.

AIMS OF THE INVENTION

One aim of the present invention is that of eliminating thedisadvantages of traditional systems and in particular of reducing themechanical stresses on the structure of the storage unit.

A further aim of the present invention is that of controlling themovement of the flexible member both in the input zone and in the outputzone so as to optimize the functioning of the line according to the rateof the gluing machine and of the cropper, even when there are greatvariations in the output frequency of the rolls from the gluing machineand the feed frequency of rolls to the cropper.

A further aim of the present invention is that of eliminating the riskof individual empty seats being intercalated between full seats.

SUMMARY OF THE INVENTION

These and other aims and advantages, which will be clear to experts inthe field from reading the text which follows, are achieved with anaccumulation storage unit of the type mentioned above, in which the twomotor units move the flexible member with a continuous motion, and inwhich the speed of advance of the two groups of seats is determined bythe rate of said first and said second section respectively.

In essence, contrary to what takes place in traditional systems,according to the invention provision is made for keeping the flexiblemember in continuous motion (at a normally non-constant speed),adjusting the transit speed of the seats of the rolls in front of theinput means and of the output means according to the rate with which therolls come from the section upstream and to the rate with which theseare requested by the section downstream of the storage unitrespectively.

The various sections of the production line are controlledelectronically by means of a programmable unit. This is capable ofknowing the production rate of the re-reeling machine and of the gluingmachine on the one hand and of the cropper on the other. On the basis ofthis information, it is possible to control the speed of the two motorunits associated with the flexible member of the storage unit. When theproduction rate of the section upstream or downstream is modified, thisimplies a modification of the speed of one or of the other motor unit(or of both).

In practice, in storage units of this type, an input distributor and anoutput distributor are provided, which transfer a log individually fromsaid first section to said storage unit and from said storage unit tothe section downstream respectively. In this case, according to aperfected embodiment of the invention, it is possible to associate withsaid input distributor and with said output distributor respectivesensor means which determine the number of rolls waiting upstream of theinput distributor and downstream of the output distributor. The advancespeeds of the two motor units, already proportional to the rates of thecropper and of the re-reeling machine (thanks to the informationoriginating from the programmable control unit or in another suitablemanner), are in this case further modified according to the number ofrolls waiting to obtain even more accurate functioning and greatertimeliness for intervention for the adaptation of the rate of chargingand discharging of the rolls onto and from the storage unit.

Thus, if, for example, the re-reeling machine increases the speed ofproduction, a greater number of rolls will leave the gluing machine perunit of time. These will accumulate upstream of the distributor forinput into the storage unit. The sensor detects the increase in thenumber of rolls waiting and consequently brings about an increase in thespeed of the first motor unit and of the input distributor for thepurpose of avoiding the accumulation of an excessive number of rollsoutside the storage unit. The opposite occurs if the re-reeling machinereduces its own speed. The same occurs in output in response to theworking speed of the cropper. The control by means of the sensors isadvantageously added to the control by means of the information on theproduction rate coming from the control unit of the re-reeling machineand of the cropper. This does not, however, exclude controlling thespeeds of the two motor units only by means of the signals coming fromthe sensors. In this case, it will be necessary to provide a greaternumber of sensors upstream and downstream of the storage unit.

Further advantages and improvements of the storage unit according to theinvention are described below.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by following the description andthe attached drawing which shows a practical non-limiting embodiment ofthe invention itself. In the drawing,

FIG. 1 shows a lateral diagrammatic view of the accumulation storageunit;

FIG. 1A shows an enlargement of the lower zone of the storage unit;

FIG. 2A shows an enlargement of the discharge zone;

FIG. 2B shows an enlargement of the zone for charging the logs into thestorage unit, and

FIG. 3 shows diagrammatically a portion of the production line.

DESCRIPTION OF THE INVENTION

The production line in which the storage unit is inserted is partiallyrepresented in a diagrammatic manner in FIG. 3, in which R indicates there-reeling machine, I the gluing machine, P the storage unit and T thecropper.

The storage unit has a frame 1 on which there are arranged four guidewheels for a flexible member 3 constituted by a pair of parallel chains.A first series of guide wheels, indicated by 5, 5A and 5B, is positionedin the upper zone of the frame 1. The wheels 5, 5A, 5B have fixed axles.A second series of guide wheels, indicated by 7, 7A and 7B, ispositioned in the lower zone of the frame 1. The wheels 7, 7A and 7Bhave fixed axles but the wheels 7 have axles which are positionallyadjustable to take up the play which is created during functioning as aresult of the lengthening of the chains forming the flexible member 3.Adjusting screws 6 and locking screws 8 make this adjustment possible bymoving the crosspiece 10 (see in particular FIG. 1A) on which the wheels7 are supported. Two series of intermediate guide wheels, indicated by 9and 11, are mounted on a moving element 13 which is vertically movablealong two uprights 15 and 17.

In the simplified representation in FIG. 1, the path of one single chainforming the flexible member 3 is indicated; the second chain is arrangedin a vertical plane parallel to the plane of the figure and is guidedaround guide wheels arranged according to the same configuration on theopposite side of the storage unit. Arranged between the two parallelchains, with constant spacing, are seats or troughs 19 with a V-shapedcross-section, only some of which are indicated in FIG. 1, while theothers have been omitted for clarity of drawing. The troughs 19 areborne in an oscillating manner by the flexible member to discharge therolls or logs L on an inclined surface 21 for charging the cropper Tarranged downstream of the storage unit P.

23 indicates a first motor unit which operate the upward movement,according to f3, of the flexible member 3. The movement according to f3is controlled so as to present the troughs 19 sequentially in front ofthe input zone of the logs L coming from the gluing machine I arrangedupstream of the storage unit.

Provided in the input zone is a distributor 25 which, by rotating,allows the passage of one roll L at a time towards the flexible member 3which--with a respective trough 19--acts to take each individual roll Land to transport it upwards.

The distributor 25 is actuated by a gear motor 26 (sketched in FIG. 2B)operated, by means of suitable timing delay, by a sensor 28 whichdetects the passage of each trough 19 to be charged. The timing delay(that is to say the delay between the emission of the signal by thesensor 28 and actuation of the gear motor 26) is variable automaticallyaccording to the speed of the motor unit 23. This makes the log L andthe trough 19 arrive contemporaneously in the charging zone.

27 indicates a second motor unit which controls the movement downwardsaccording to f3' of the discharge branch of the flexible member 3. Inthe downward movement according to f3' of the flexible member 3, eachtrough borne by the latter encounters a cam surface 29 which interactswith a feeler 31 on the trough 19 (FIG. 2) to bring about itsoscillation and consequently the discharge of the log L onto theinclined surface 21. The cam surface 29 constitutes the means ofdischarge or of output of the rolls towards the cropper. The motor unit27 is controlled so as to discharge the logs L onto the inclined surface21 with a frequency according to the working speed of the cropper Tdownstream, the channels for advance of the log of which are indicatedby 33.

The moving element 13 makes it possible to have different speeds for thetwo motor units 23, 27, so that the frequency of arrival of the logs atthe gluing machine can be different from the frequency of discharge ontothe inclined discharge surface 21. The troughs 19 borne by the flexiblemember 3 and positioned above the moving element 13 are full. Also fullare the troughs arranged along the ascending branch on the charging side(on the left in the drawing) and along the descending frame on thedischarge side (on the right in the drawing) above the inclined surface21. The remaining troughs are empty. When the frequency of arrival ofthe rolls is greater than the discharge speed, the moving element 13 islowered, increasing the number of full troughs and reducing the numberof empty troughs. The opposite occurs when the request for logs by thecropper increases in relation to the number of logs arriving from thegluing machine.

The descending end branch (on the right in FIG. 1) of the flexiblemember is guided, apart from around the guide wheels 5B and 7B, alsoaround two wheels 35, 37 with a fixed axles and a third wheel 39 borne(see in particular FIG. 2) by an oscillating arm 40, fulcrumed at 41 onthe frame of the machine. Associated with the arm 40 is an actuator witha cylinder/piston 43, fulcrumed at 45 on the frame and at 47 on the axleof the guide wheel 39. The actuator 43 tends to make the arm 40 rotatein the anticlockwise direction, tensioning in this manner the flexiblemember 3. Although only one actuator 43 and only one oscillating arm 40are visible in the simplified representation in the drawing, it isintended that a wheel 39 with the associated oscillating arm and theassociated actuator is provided for each of the two parallel chainswhich form the flexible member 3 on each of the two sides of the storageunit.

During the functioning of the storage unit, the play which is generatedon the flexible member 3 as a result of wear and which causes alengthening of the member itself is taken up by the tensioner formed bythe wheel 39, by the arm 40 and by the actuator 43, constantly underpressure, until the limit position of the wheel 39, indicated by 39X, isreached. In this position, which can be detected by a sensor means, forexample a micro-switch 49, against which the actuator 43 or the arm 40comes to bear, or a magnetic sensor acting directly inside the actuator43, an alarm signal is emitted, and the production line is if necessarystopped until the operator has acted to adjust the position of the lowerguide wheels 7, thus bringing the arm 40 into the initial position inFIG. 2.

The first motor unit 23 moves, by means of the wheel 7A, the flexiblemember 3 with continuous motion, at a speed which is determined andvariable according to the rate with which the logs L come from there-reeling machine R and from the gluing machine I. Correspondingly, therotating distributor 25 rotates in an intermittent manner so as todeposit a roll L on each seat or trough 19 in transit. The adjustment ofthe speed of advance of the motor unit 23 and consequently of therotation of the rotating distributor 25 can be obtained directly fromthe production data coming from the re-reeling machine R which iscontrolled by its own central unit. On the other hand, or incombination, sensor means 61 can be provided, which detect the number oflogs L1, L2, L3 waiting on the chute 63 upstream of the rotatingdistributor 25. The speed of translation of the first ascending branchof the flexible member 3 and therefore the frequency of rotation of therotating distributor 25 are modified according to the number of logs L1,L2, L3 waiting. If this number exceeds a predetermined number, the speedof the motor unit 23 and therefore the rate of the rotating distributor25 are temporarily increased to bring the number of logs waiting back tothe predetermined number. The opposite occurs if the number of logs L1,L2, L3 falls below a predetermined limit.

Similarly, in output--at the end of the inclined surface 21--a rotatingdistributor 22 is provided, which is operated by the cropper T accordingto its own production requirements. This allows the rhythmical passageof the logs to the cropper T. The speed of rotation of the second motorunit 27, which determines the frequency of discharge of the rolls ontothe inclined surface 21, is also according to the operating speed of thecropper T. This speed can be detected directly from the data of thecentral control unit. In this case also, in addition or as analternative to direct control by means of the operating speed of thecropper, which is known by the central unit, control of the speed ofadvance of the second motor unit 27 can be obtained by means of usingsensor means 24 according to the number of logs L waiting on theinclined surface 21, with methods similar to those illustrated forcontrol of the motor unit 23.

In this manner, regular functioning is obtained, without suddenunexpected starts and stops of the flexible member 3 and therefore witha considerable reduction in the dynamic stresses on the members of themachine. At the same time, a regular afflux of rolls to the cropper T isguaranteed, with consequent elimination of the risk of the absence of aroll in one or more of the working channels of the cropper and of thenegative consequences on the functioning of the line which were pointedout above.

It is intended that the drawing shows only an exemplification given onlyby way of practical demonstration of the invention, it being possiblefor this invention to vary in form and arrangement without, however,leaving the scope of the concept which forms the invention itself. Anypresence of reference numbers in the attached claims has the purpose offacilitating reading of the claims with reference to the description andto the drawing and does not limit the scope of protection represented bythe claims.

I claim:
 1. A storage unit for temporary storage of rolls, arrangedbetween a first section and a second section of a production line andcomprising:an endless flexible member defining a closed path within saidstorage unit and bearing a plurality of seats for said rolls, said seatsbeing subdivided into a first group of empty seats and a second group offull seats; an input feeder for controlled distribution of rollsarriving from said first section to said seats of said first group; anoutput feeder for controlled discharge of rolls from said seats of saidsecond group toward said second section; a first motor for advancingsaid seats of said first group toward said input feeder; and a secondmotor for advancing said seats of said second group toward said outputfeeder; wherein said first motor and said second motor have first andsecond independently adjustable continuous speeds, respectively; saidfirst motor and said second motor move said flexible member at acontinuous variable speed; and said first and second independentlyadjustable continuous speeds are adjusted based on a rate of rollarrival from said first section and a rate of roll request from saidsecond section, respectively.
 2. The storage unit of claim 1, whereinsaid input feeder includes an input distributor to transfer rollsindividually from said first section to said storage unit, and saidoutput feeder includes an output distributor to transfer rollsindividually from said storage unit to said second section.
 3. Thestorage unit of claim 2, wherein a first sensor is associated with saidinput distributor to count rolls waiting upstream of said inputdistributor and a second sensor is associated with said outputdistributor to count rolls waiting upstream of said output distributor,and wherein speed of advance of each of said first motor and said secondmotor is dependent on the number of rolls waiting upstream of said inputdistribution and said output distributor, respectively.
 4. The storageunit according to claim 1 or 2, wherein said speed of each of said firstmotor and said second motor is adjusted based on signals received fromeach of said first section and said second section, respectively, saidsignals being based on a rate of production of each of said firstsection and said second section, respectively.
 5. The storage unit ofclaim 2, further comprising a sensor capable of detecting passage of anempty seat in a predetermined position upstream of said inputdistributor, wherein said sensor emits an operating signal for actuationof said input distributor to transfer a roll into said empty seat, saidactuation occurring with a delay in relation to emission of said signal,said delay being dependent on the speed of said first motor.
 6. Thestorage unit of claim 1, 2, or 3, wherein said flexible member bears aplurality of oscillating seats and is guided by two external series offixed wheels and two internal series of movable wheels, said twointernal series being movable to modify a length of a piece of saidflexible member bearing said first group of seats in relation to alength of a piece of said flexible member bearing said second group ofseats.